非限制性定语从句which后面引导的句子可以用动词的复数形式吗?

这个问题好像存在好久了,说下自己的看法吧. 仅供参考.
which在非限制性定语从句中,用来指主句内容.
He made noise in class, which made his teacher angry.
这个句子其实= He made noise in class and it/ that made his teacher angry.
显然it或that, 应该指上文发生的事情,或上文的情况.这里表现的比较含糊,没有数量之分,所以我觉得which后面不能用复数谓语动词.
上面一个句子改成：He often makes noise and sleeps in class, which makes his teacher angry.
这里我觉得还是用单数谓语动词.
改成He often makes noise and sleeps in class and it/that makes his teacher angry.
不能说He often makes noise and sleeps in class and they/those make his teacher angry.
显得不伦不类.